what is checksum????

[edgar]

PEACE!!

hello everybody!!!

could you please educate me or give me an idea what is a checksum ? and how does it affect the operations of the phone?

best regards
edgar

[gkagg]

Generally, checksum is a simple error-detection scheme in which each transmitted message is accompanied by a numerical value based on the number of set bits in the message. The receiving station then applies the same formula to the message and checks to make sure the accompanying numerical value is the same. If not, the receiver can assume that the message has been garbled.

The application of checksum on mobile phones has to do with the code their firmware is written and the way through which the possible data errors are corrected... When we apply a change or a modification into a mobile phone's software (aka flash) some data changes and the algorithm of the mobile phone thinks that the code has been altered or there has been an error. In order to fix this error we correct the checksums(...the numerical value as stated above...) before we flash our phone, so the receiver (in this example, the mobile phone) thinks that the received data are phenomenically not altered or damaged.So when we modify the flash file of a mobile phone we MUST correct the checksums before we flash it back to our phone or else we wil receive an error.
Hope I was comprehensable!

[NokDoc]

Hi,

Nokia's have 3 sorts.

- The McuChk, which is written to two locations in the file.

- The 8/9 ppm checksums per ppm chunk.

- the Flash chk, used for calculation of Faid nr.

The effect of the first two incorrect is a CS.

An incorrect FlashChk leads to no network & reboot symptoms.

NokDoc

[filka97]

to correct checksum use this: